This invention relates to gas discharge devices which utilize a cathode and dielectric spacer having a single hole or an array of holes therein and an arbitrarily shaped anode, and methods of use thereof.
Optical lithography is used e.g. by the semiconductor industry to generate the small features which determine the size of the electronic circuits on semiconductor wafers. Mercury arc lamps have been used as light sources for such photolithography.
In order to reduce chip feature sizes excimer laser have been used such as the 248 nm KrF laser. Excimer lasers used for deep-UV photolithography are discharge pumped. Efficiencies are on the order of one percent to two percent. They only exist as pulsed devices with pulse duration of tens of xcexcs determined by the plasma stability. Voltages required to operate them are in the multi-kV range.
Non-coherent excimer radiation and other sources of monochromatic vacuum ultraviolet (VUV) light are also being explored. Excimers are temporary chemical compounds composed of atoms which under normal conditions would not form a stable molecule. A stable excimer molecule is only formed in a high-energy, or excited, state. The excimer molecule as a whole decays into the constituent atoms upon emission of characteristic radiation. Excimers have been produced e.g. by applying beams of energized particles to inert gases. The gas is present under substantial pressure. Another means of producing excimers are high-pressure discharge plasmas such as e.g. plasmas produced in microhollow (MHC) cathode discharges.
The present invention provides a method and apparatus for the production of intense hydrogen Lyman-a as well as Lyman-xcex2 emissions and other atomic emissions from a microhollow cathode (MHC) discharge operated in a mixture of high-pressure Neon (Ne), Helium (He), or Argon (Ar) with a small admixture of Hydrogen (H2), Nitrogen (N2, or Oxygen (O2).
An object of the present invention is to provide a light source comprising a sealed, light-transmissive tube containing high pressure gases or high pressure gas mixtures at a high pressure (100 Torr to 10,000 Torr) with a discharge device consisting of a first conducting electrode (cathode) having a single hole or a plurality of holes therein and a second conducting electrode (anode, which may or may not have a hole or holes similar to the one(s) in said first electrode), mounted within said tube and separated from first electrode by an insulating spacer with a hole or holes therein similar to hole(s) in said first electrode; and electrical means for coupling electrical energy to said first and second electrodes for producing discharges in each of the holes in said first electrode. The exact shape of the hole(s) in said first electrode and the insulating spacer are not important as long as the area of the hole(s) is in the range from 0.001 mm2 and 1 mm2 (microhollow cathode (MHC) discharge).
Another object of the present invention is to provide a method of generating intense hydrogen Lyman-a or Lyman-xcex2 or atomic oxygen and nitrogen emissions in the spectral range from 100 nm to 150 nm by placing the MHC discharge device into a container which contains a high pressure gas or high pressure gas mixture.
Another object of the present invention is to provide a method of generating an extended source of higher irradiance over an extended area by using an array of MHC discharge sources operated in parallel.